Bore calibrating stamp



Dec. 9, 1958 KKKLOPFER 7 2,863,209

BORE cAnIBRA rI'nG STAMP Filed April 19, 1955 United States Patent BORECALIBRATIN G STAMP Karl Klopfer, Wil, St. Gallen, Switzerland, assignorto K. Klopfer A.-G. Werkzeugund Maschinenfabrik, Bronschhofen, St.Gallen, Switzerland Application April 19, 1955, Serial No. 502,361Claims priority, application Switzerland April 20, 1954 2 Claims. (Cl.29-90) The present invention relates to a bore calibrating stamp servingto finish pre-machined bores at a desired accurate diameter.

The production of bores of accurate diameter in the metal industry stillpresents many difficulties. A number of tools, such as reamers, areknown by means of which the bores may be finished. The quality of thesurface and the accuracy of the bore diameter which may be obtained byusing such tools, is, however, not always suflicient. It is also knownto press balls or ball-shaped stamps into these bores in order tosmoothen their surfaces. The use of such tools may some times be veryadvantageous. They have, however, the draw-back that a high pressure isnecessary to force the tool into the bore. This may give rise to unduedeformations of the work piece. In addition the bores may only haveslight variations or deviations from a pre-machined diameter, since thematerial is only pressed by such tools, which have no cutting efiect.

An object of the present invention is to provide a calibrating stampwhich will prevent deformations in the work piece due to pressureapplied by the calibrating stamp when the latter is pressed through thebore.

A further object of the present invention is the provision of a borecalibrating stamp having in addition to a calibrating surface a forwardcutting edge adapted to cut material from the walls of a bore when thecalibrating stamp is pressed therethrough.

A still further object of the present invention is the provision of acalibrating stamp comprising a rear cutting edge by means of which asecond finishing operation may be carried out when the stamp is drawnout of the bore 'in a direction opposite to the one in which it waspressed in.

Further objects and advantages of the present invention will becomeclear from the following description and the appended claims in whichthe features believed to be characteristic are set forth.

In order that the invention may be better understood and put intopractice, one embodiment thereof will hereinafter be described by way ofexample and with reference to the accompanying drawings, in which:

Fig. 1 shows a side view of the calibrating stamp and Fig. 2 shows aview of the stamp as seen from below.

The calibrating stamp shown in the drawing comprises at its front end acylindrical calibrating face 2 adjacent to the ends of which two taperedannular faces 3 and 4 are arranged to include an angle of 45 with thecalibrating face 2. The front annular face 3 has flat face portions 5,which include the same angle of inclination with the calibrating faceand are equally spaced over the circumference of the tapered annularface 3. These fiat face portions 5 intersect the calibrating face alongbent lines which form cutting edges 6 of corrugated configuration.Between the calibrating face 2 and the rear annular face 4 a cuttingedge 7 is arranged which is situated in a plane perpendicular withrespect to the axis of the calibrating stamp 1.

, here is to have in its finished state.

The described calibrating stamp functions as follows:

In order to use the calibrating stamp, the bore must first be machinedto a diameter which is about 0.05 mm. smaller than the desired accuratediameter, which the This pro-machined bore may have uneven portions inits surface. If the calibrating stamp described, is pressed through sucha bore, for instance by means of a hand press, a small drill or a turretlathe in the direction of the arrow, material is cut away from the wallsof the bore by means of the cutting edge 6. If this cutting edge werenot corrugated, i. e. if the latter were situated in a planeperpendicular with respect to the axis of the stamp, such as the edge 7,the lateral grooves made by previous machining operations in the borewould influence the stamp such that the bore surface obtained would haveslight corrugations. By means of the corrugated configuration of thecutting edge 6, the uneven portions in the pre-machined bore may beremoved. These uneven portions therefore have no adverse effect upon thequality of the finished bore. Since the cutting angle of the edge 6 isnegative, the material will be pressed to a small extent thus producinga smoothing of the bore surface. Due to the front tapered face 3 thestamp 1 will center itself when being pressed through the bore.

If the stamp 1 is drawn back out of the bore opposite to the directionindicated by the arrow, the bore will be smoothened completely, thusremoving all uneven portions from the bore surface.

Bores which are finished in the described manner by means of thecalibrating stamp according to the invention will be absolutely accuratein their diameter the.

machining tolerance being in the order of only about 0.005 mm. Inaddition the surface of the bore obtained thus, will be very smooth. Nochecking of the bore by means of a caliper gage is necessary afterfinishing, since deviations from the desired diameter may be found bymeans of the calibrating stamp. If the diameter is too large, the stampmay be introduced too easily into the bore thus showing that the workpiece is to be excluded. If the pre-machined bore is too small in itsdiameter, the latter will be finished to the desired accurate measuresuch that the piece must not be subjected to an additional machiningoperation. Further it is possible to work with double the operatingspeed possible if the pieces were checked by means of a calipengage.

The calibrating stamp according to the invention has the advantage topermit finishing of bores having very thin Walls, since the material ismainly machined off, while with previously used tools, such as balls orround stamps, which only smoothen the bore, such pieces of small wallthickness will be unduly enlarged.

If a number of different stamps of successively larger diameter areused, a bore may be enlarged to any desired measure.

I claim:

1. A bore calibrating stamp comprising a shaft, a cuttinghead on an endof the shaft, a cylindrical calibrating face arranged circumferentiallyon the cutting head, a tapered annular face adjacent one end of thecalibrating face, a corrugated cutting edge situated intermediate thesaid cylindrical calibrating face and said tapered annular face, asecond tapered annular face adjacent the other end of the calibratingface, and a circular cutting edge situated intermediate the saidcylindrical calibrating face and said second tapered annular face, saidcorrugated cutting edge and said circular cutting edge beingrespectively effective upon movement of the stamp into and out of thebore for cutting and smoothing action.

2. A bore calibrating stamp comprising a shaft, a cutting head on an endof the shaft, a cylindrical calibrating face arranged circumferentiallyon the cutting head,

a tapered annular face adjacent to an end of the calibrating face, fiatportions on said tapered annular face and equally spaced over thecircumference thereof, a corrugated cutting edge at the intersection ofsaid flat portions with said cylindrical calibrating face, a secondtapered annular face adjacent to the other end of the calibrating face,and a circular cutting edge situated intermediate said cylindricalcalibrating face and said second tapered annular face, said corrugatedcutting edge and said rear circular cutting edge being respectivelyefifective upon movement of the stamp into and out of the bore forcutting and smoothing action.

References Cited in the file of this patent UNITED STATES PATENTSBunting May 16, 1916 Donaldson Dec. 7, 1920 Loomis Sept. 4, 1923Harrison Nov. 21, 1939 Githens Feb. 4, 1941 Weaver Mar. 4, 1941 BlazekNov. 13, 1945

